The invention relates to an electric handheld core drilling device, a diamond core bit and a handheld core drilling system with an electric handheld core drill and a diamond core bit.
A known-from-the-prior-art electric hand-held core drilling device has a tool receptacle for receiving a diamond drill bit, wherein the tool receptacle has a receiving sleeve and a tool receiving piece disposed therein, which is driven during operation of the hand core drill around an axis of rotation in the operating direction, and with a compression spring arrangement, which is arranged within the receiving sleeve and which supports the receiving sleeve and the tool receiving piece resiliently against each other.
The receiving sleeve has a central insertion opening through which an insertion end of the diamond drill bit can be inserted into the tool receiving piece when the insertion with respect to the insertion in a insertion rotation position and the compression spring arrangement is pressure-loaded.
The insertion end is secured in the central insertion opening against withdrawal coaxial with the axis of rotation when the insertion end is located in the tool receiving piece and with respect to the insertion in a locking rotational position and the compression spring arrangement is relatively less pressure-loaded.
On the receiving sleeve along a circumferential direction of the insertion opening, three equally spaced retaining tabs are formed, each having a stop surface, which respectively face the tool receiving piece, wherein the insertion end, if this is secured against withdrawal coaxially with the axis of rotation, by means of three contact surfaces formed on the insertion end, abuts the stop surfaces.
Under a rotational position for insertion, in the context of the present invention, such a rotational position of the insertion end, based on the axis of rotation to be understood in which the three retaining bolts, which are preferably equally spaced along a circumferential direction of the insertion end at the insertion end, at the retaining tabs of the receiving sleeve, can be inserted unhindered in the axial direction in the central insertion opening.
Under a blocking rotational position in turn one means, based on the rotational axis, to the insertion rotational angle of the insertion end. In this blocking rotational position, pulling out the insertion end from the receiving sleeve is impossible due to the retaining bolt whose path is blocked by the retaining tabs.
It is an object of the present invention to provide an electric handheld core drill which favors a quick bit change and a low-wear operation.
This object is achieved in that along a circumference of the tool receiving piece exactly three equally spaced bearing surfaces are formed on the tool receiving piece, each facing the stop surfaces, wherein the bearing surfaces in turn, based on the stop surfaces, oppositely-oriented axial stop for the insertion end of the diamond drill bit which is in the rotational blocking position, formed by means of mating bearing surfaces on the insertion end, wherein from the bearing surfaces, the bearing surfaces each delimiting one side, exactly three evenly spaced studs protrude, on each of which a stud surface is formed whose respective surface normal is oriented perpendicular to the axis of rotation and tangential to the circumferential direction, so that a torque transmission in the operating direction of rotation from the tool receiving piece to the insertion end, if this is in blocking rotational position and the compression spring arrangement is comparatively less pressure-loaded, exclusively by positive engagement between the three stud surfaces and corresponding stud mating surfaces at the insertion end takes place, wherein each of the three stud surfaces in the radial direction are at most half as wide as a respective bearing surface in the radial direction.
The invention includes the realization that the torque which can be transmitted by the tool receptacle can be increased by the stud surfaces according to the invention. This be a spring force of about 1600 N in a disc spring arrangement.
Characterized in that according to the invention, each of the three stud surfaces in the radial direction is at most half as wide as a respective stop surface in the radial direction, at the same time preventing jamming of the insertion end in the tool receiving piece as far as possible.
By means of the stud surfaces provided according to the invention, there is a decoupling between torque transmission in the operating direction of rotation and spring force action of the compression spring arrangement along the axis of rotation.
In a particularly preferred embodiment, the stop surfaces are formed flat, so that they form a sliding contact with the corresponding contact surfaces at the insertion end and thus, at least in the area of the stop surfaces between the receiving sleeve and insertion end in the blocking rotational position, a rotational degree of freedom around the axis of rotation remains unsecured.
In other words, the insertion end and the receiving sleeve are not rotationally secured relative to each other via an anti-twist device in the area of the stop surfaces. If, at least between the receiving sleeve and the insertion end, a rotational degree of freedom about the rotational axis remains unsecured in the area of the stop surfaces, this does not exclude that an actual relative twisting between the receiving sleeve and the insertion end is ensured upon rotation in the operating direction of rotation. In fact, this is required for the torque transfer between the tool receiving piece and the insertion end.
Due to the fact that at least between the receiving sleeve and the insertion end in the area of the stop surfaces with the insertion end located in the blocking rotational position, preferably a rotational degree of freedom about the rotational axis remains unsecured, so that an adhesion of the insertion end and the receiving sleeve, which is undesirable for the removal of the diamond drill bit, is avoided. The fact that in this embodiment, both the stop surfaces and the corresponding contact surfaces are configured free of locking means or the like, an undesirable accumulation of construction dust, which can lead to such arrest, largely avoided.
It has proven to be advantageous if the studs each have a plateau, which is spaced from the stop surface. A respective surface normal of the plateau may be oriented parallel to the axis of rotation. Preferably, a respective stud surface is perpendicular to the respective plateau and may limit a stud tip. Preferably, a stud tip extends from the plateau in the direction of the respective retaining tab.
It has proven to be advantageous if the stud tip extends along at least one third of the plateau along a rotational axis of the closest circumferential portion of the stud. Preferably, the stud tip extends over at most two thirds of the plateau along the circumferential axis of rotation of the stud closest to the axis of rotation.
In a further preferred embodiment, a respective one of the three stud surfaces extends in the radial direction at most half as wide as a respective plateau in the radial direction. This can significantly reduce unwanted jamming of the male end in the tool receptacle be a torque-intensive operation.
It has proved to be advantageous if a side wall extending in the radial direction of a respective stud, which preferably extends between a respective plateau and a respective bearing surface, is inclined at 30° to the axis of rotation.
It has been found to be advantageous that the compression spring assembly when the insertion end is located in the tool receiving piece and is located with respect to the insertion end in a blocking rotational position, wherein the compression spring arrangement exerts a spring force of about 1600 N between the tool receiving piece.
A (higher) pressure-loaded state of the compression spring arrangement is to be understood to mean the state of the compression spring arrangement, in which the compression spring arrangement is compressed. This is the case when the receiving sleeve is pressed in the direction of a male diamond drill bit to enable threading the three retaining bolts formed at the insertion end of the three on the flat tabs past and through the insertion opening. Such pre-pressing of the receiving sleeve can be realized for example by a pressure plate provided on a housing of the handheld core drilling device with an associated pressure lever.
A comparatively less pressure-loaded state of the compression spring arrangement is understood to mean such a state of the compression spring arrangement, in which the compression spring arrangement is less compressed compared to the compressed state. This is the case when the receiving sleeve, with inserted insertion end, is in its original position, in which no external pressure, for example, by a pressure plate of the electric handheld core drilling device is exerted on the receiving sleeve. In this state, the stop surfaces formed on the retaining tabs are subjected to pressure on the corresponding contact surfaces at the insertion end.
It has proven to be advantageous if the compression spring arrangement consists of five series-connected disc springs. Preferably, the spring force is approximately 1600 N, which the compression spring arrangement exerts on the tool receiving piece by a corresponding equivalent spring constant of the five series-connected disc springs at a given extension.
It has proven to be advantageous if the tool receptacle has a sealing ring consisting of an elastically deformable plastic. Preferably, the plastic has a Shore hardness of less than 25. This can reduce any preload losses when clamping the drill bit. Preferably, the sealing ring is disposed within the tool receiving piece, more preferably, the sealing ring is supported against the insertion end, if this is located in the tool receiving piece.
In a further preferred refinement, a knurl is formed on an outer surface of the receiving sleeve, such that the receiving sleeve rotates annularly. Preferably, the knurl forms exactly a closed ring which, based on the axis of rotation over extends at least one third and at most two thirds of the length of the receiving sleeve.
The invention is also solved by a diamond bit, in particular for a prescribed hand-held core drilling device. The diamond drill bit has exactly one insertion end passing through a central insertion opening into the tool receiving piece of the handheld core drilling device. At the insertion end, preferably circumferentially uniformly spaced from each other, exactly three retaining bolts are formed, which are provided for engagement with retaining tabs, which in turn are formed on a receiving sleeve enclosing the tool receiving piece
The retaining bolts may each have a contact surface which corresponds to a stop surface on the respective retaining tabs. Particularly preferably, each of the retaining bolts has a mating bearing surface whose surface normal runs in each case parallel to the axis of rotation.
Preferably, three equally spaced stud mating surfaces are formed at the insertion end along the circumferential direction, which may be perpendicular to the respective mating bearing surfaces and which are preferably set against a peripheral edge surface of the retaining bolt.
Particularly preferably, the contact surfaces are formed flat, so that they form a sliding contact with the corresponding stop surfaces on the retaining tabs and thus, at least between receiving sleeve and insertion end in the region of the contact surfaces located in the insertion end located in a blocking rotational position, a rotational degree of freedom around the axis of rotation remains unsecured.
The diamond bit may be further developed by features already described with respect to the handheld core drilling device.
The invention is also solved by a handheld core drilling system having a previously described hand core drilling device and a diamond core bit as described above.
Further advantages arise from the following description of the Figures. In the Figures, various embodiments of the present invention are shown. The Figures, the description and the claims contain numerous features in combination. The person skilled in the art will expediently also consider the features individually and combine them into meaningful further combinations.
In the Figures, the same and similar components are numbered with the same reference numerals.